# repository.py
class UserRepository:
    def __init__(self):
        self.users = {}

    def save_user(self, card_id, user):
        self.users[card_id] = user

    def get_user(self, card_id):
        return self.users.get(card_id)

    def delete_user(self, card_id):
        if card_id in self.users:
            del self.users[card_id]
            return "账户已注销成功。"
        return "该卡号不存在。"
